there are some maps that are available for this region, which are free to download and here i will post some of my thoughts about them.
i did field and GPS testing of those maps considering Serbia and Montenegro region: http://web.uni-plovdiv.bg/vedrin/index_en.html#section2
this map is available in version for LOCUS also. It is 1,7gb and covers most eastern and south part of Serbia, including Bulgaria(whole) and whole Macedonia. Their source was obviously soviet military maps in scale 1:500000
map is seamless, and precise in Serbia. Relief is bit hard to read and on some parts it is unclear.
Maps are good looking,and very fast to read on a blink of an eye. Forest coverage is good since those maps are obviously made by processing satellite data.They are made in geopdf format which take small space but you need global mapper program to convert them to ozi format then mapc2mapc to convert them to locus.
They are good for foreigners which travels into Yugoslavia back country, but for locals they are inaccurate ~25-60m are offsets.Offset get smaller when you go west.
Russian raw version:http://loadmap.net/
it have same looking and accuracy as before mentioned Bulgaria (in begining of the post) but you have variety of scales:1:1M-1:50K larger scales are pretty inaccurate but since they are totally free they are good for region.
They also lack locus version, they are gif files accompanied with ozi map file so you will need MAPC2MAPC program to convert them into locus.
there is no yet place to download them but i am working on that(making locus versions)
as somebody who live here and go in mountains a lot, my votes are as follows:
1. Yugoslav military maps 50k scale for everything except new roads for cars and forest coverage(use google satellite or ovi Nokia for that), but for bicycle , walking, hiking, they are the BEST
2. American topo maps for quick view, and for overview of "newer" road data, forest coverage, explanation of toponym, conversion to statute measure.
3. russian/ bulgarian it is on 3rd place mostly because majority of territory is not covered with 50k scale but with 100k scale or larger